Science China Materials最新文献

It has made significant progress in catalyst and reactor design for commercial current densities in CO₂ electroreduction (CO₂ER). However, these catalyst systems have rarely been applied for a C₂ gas product of ethane due to its commonly inferior selectivity relative to other C₁ and C₂ products. Herein, bamboo-like amorphous Ni(OH)₂ nanotubes wrapped Cu nanoparticles composite (Cu NPs@a-Ni(OH)₂ NTs) is constructed for selective CO₂ER to ethane in a flow cell. The unique Cu NPs@a-Ni(OH)₂ NTs structure provides a confined geometry to improve the adsorption of the reactive species. The interface of Cu NPs and a-Ni(OH)₂ NTs is stabilized by generating some NiOH species. The produced Cu@NiOH interface enhances the activation of CO₂ to *C*OOH and strengthens the adsorption of *CO_L on Cu site for more *COH formation and its dimerization for final ethane production. Meanwhile, amorphous Ni(OH)₂ nanotubes promote water dissociation for the hydrogenation of carbonous intermediates, contributing to ethane production. The synthesized Cu NPs@a-Ni(OH)₂ NTs can reach a Faradaic efficiency of 48.3% and a partial current density of −226.7 mA cm⁻² for ethane at −0.7 V in a flow cell, with a remarkable stability for 24 h. This work provides a rational strategy to engineer Cu-based composite for selective CO₂ER to ethane in a flow cell.

Accurate detection of multiple small end-metabolic biomarkers is more sensitive than large biomolecules to provide real-time feedbacks of physiological/pathological state, but is more challenging due to lack of specific identifying groups. Current optical platforms suffer from unsatisfactory resolutions to differentiate each target because they produce similar output to different targets using a single excitation, and inevitably involve non-functional components that increase chances of interacting with non-target molecules. Herein, by taking full advantage of each building unit’s functionality to integrate multivariate recognition elements in one interface, a dual-excitation-driven full-component-responsive metal-organic framework (MOF)-based luminescent probe, namely CeTMA-TMA-Eu, is successfully custom-tailored for detecting both pseudouridine (ψ) and N-acetylaspartate (NAA), the diagnostic hallmarks of cancer and neurodegenerative disorder. Remarkably, ψ interacts with MOF’s organic building unit (trimesic acid, TMA) and filters out its absorptions of 262 nm-light to reduce its energy transferred to Eu³⁺, while NAA induces the valence transition of Ce⁴⁺/Ce³⁺ nodes to improve the cooperative energy transfer efficacy from TMA and Ce³⁺ to Eu³⁺. As a result, this platform exhibits completely reverse photoresponses towards ψ (“switch-off” at 262 nm excitation) and NAA (“switch-on” upon 296 nm excitation), and demonstrates excellent selectivity and sensitivity in complex biofluids, with low detection limits of 0.16 and 0.15 µM, and wide linear ranges of 0–180 and 0–100 µM, respectively. Such full-component-responsive probe with dual-excitation-mediated reverse responses for multi-small targets intrinsically minimizes its interaction with non-target molecules and amplifies resolution to discriminate each target, providing a new strategy for improving assay accuracy of multi-small biomarkers in diagnostics.

Electrochemical reduction from nitrate into ammonia is a chance for nitrate removal from drinking water, while at higher concentrations, this 8-electron reduction process could even become relevant for energy storage, high conversions and low onset potentials assumed. Herein, we report the synthesis and analysis of a NiFe₂O₄/C-MS hybrid system made by a molten-salt strategy where the Ni-Fe oxide spinel nanoparticles act as the active center for electrochemical nitrate (NO₃⁻) reduction reaction, while the microporous carbon serves as a conductive support to form a cohesive electrode material. The NiFe₂O₄/C-MS catalyst achieves a maximum NH₃ yield rate of 5.4 mg mg_cat⁻¹ h⁻¹ and Faradaic efficiency of 98% at −0.6 V versus reversible hydrogen electrode. With NiFe₂O₄ nanoparticles buried into microporous carbon, the onset potential decreases dramatically. We propose that this reduction originates from charge redistribution in NiFe₂O₄ in the electronic heterojunction with carbon, while enhanced electrolyte diffusion in microporous carbon facilitates high conversion rates. Density functional theory calculations clarify the low energy barrier on NiFe₂O₄, highlighting the essential role of Ni in activating Fe species. The COMSOL Multiphysics simulations demonstrate that the microporous curled carbon accelerates NO₃⁻ transport and enhances adsorption on the reactive sites. This work offers insights for designing carbon-based nanocomposites for efficient nitrate reduction electrocatalysis.

Transparent conductors (TCs) have widespread applications in the fields of modern photodetectors and smart windows. While TCs for visible wavelengths have seen significant advancements, the development of visible-infrared (vis-IR) broadband TCs for infrared is still a daunting challenge due to the trade-off between infrared transparency and conductivity. Here, we present a vis-IR TC fabricated by using a damage-free indirect transfer method. This method involves polymer-mediated bonding of a high-resolution, standalone copper (Cu) mesh onto infrared or visible substrates via a transfer film. The obtained Cu mesh TC exhibits excellent conductivity with a sheet resistance as low as 0.06 Ω/□, as well as 81% transmittance at a visible wavelength of 550 nm and 65% transmittance at an IR wavelength of 10 µm. Furthermore, a specially developed bonding strategy ensures the long-term reliability of the Cu mesh TC in harsh environments. The Cu mesh TC can be applied in both heating and electromagnetic (EM) shielding. As a transparent heater, it reaches approximately 100°C at an applied voltage of 1.2 V within 100 s. For EM shielding, a demonstration using a stainless-steel box with a transparent observation window which is integrated with the Cu mesh shows that while the window allows both optical and IR observations, the 4G signals (8.2 GHz) of a smartphone inside the box are effectively blocked.

Magneto-conductance (MC) was used as a fingerprint detection tool to contactlessly visualize high-temperature evolution processes of exciplex (EX) states in the TBRb/C₆₀ planar-heterojunction (PHJ) organic light-emitting diodes (OLEDs). Specifically, MC was used to contactlessly observe at room temperature around 300 K. The reverse intersystem crossing (RISC) process from triplet to singlet EX states (EX₃→ EX₁) in the device at 300 K is observed for the first time from the TBRb/C₆₀ PHJ-OLED. The device shows a half-band-gap turn-on photoelectric characteristics. Temperature-dependent MC traces of the device present an interesting conversion from RISC to triplet-charge annihilation (TQA) process between EX₃ and charge carriers (T₁ + q → e + h + q′) after the device temperature increasing from 300 to 425 K via in-situ heating. By comprehensively analyzing MC traces, current-voltage characteristic curves, transient electroluminescence spectra, and optical microscopy images of the device and atomic force microscopy images of the TBRb film, we find that the increase of temperature destroys the molecule structures of organic materials, which leads to the generation of many traps inside the organic semiconductor films comprising the TBRb/C₆₀ PHJ-OLED. These traps will capture polaron-pairs, EX, and exciton states and then affect their interactions, which finally induces the changes of MC traces. This work not only deepens understandings of high-temperature evolution processes of polaron-pairs, EX, and exciton states in the TBRb/C₆₀ PHJ devices, but also provides a new method to study the microscopic mechanisms in OLED operating in high temperature environment.

Constructing an information storage or communication system, where countless pieces of information can be hidden like a canvas and revealed on demand through specific stimuli or decoding rules, is significant. In the present study, we developed a hydrogel canvas that leverages non-covalent interactions to induce phase separation in the polymer matrix, creating various “paintings”, including custom messages, using different chemical inks. Our strategy focuses on designing small molecule inks, with varying affinities with the hydrogel and specific responsiveness to stimuli, to achieve multiple changes such as color shifts, fluorescence emission, and dynamic optical image evolution. This skips the typical design approaches, such as incorporating responsive fluorophores into polymers for color emission through grafting or copolymerization, and thus avoids the complex processes involved in modifying and synthesizing functional polymers, along with the uncertainties in material properties that these processes bring.

Sensors with enhanced biocompatibility, high sensitivity, and stable output have gained prominence with the rapid advancement of piezoresistive sensor technologies. However, conventional piezoresistive sensors struggle to balance sensitivity and output stability. Here, we fabricated synergistic methylcellulose/chitosan MXene-based (MC/CS@MXene) aerogels through physical blending and freeze-drying, emulating the hollow bamboo structure. The aerogels form synergistic interconnection via electrostatic adsorption and hydrogen bonding, endowing the aerogel-assembled resistive sensor with high sensitivity (2.90 kPa⁻¹), exceptional mechanical stability (8000 compression cycles at 10 kPa), and rapid response and recovery times (119 and 91 ms, respectively). A piezoresistive sensor array based on MC/CS/@MXene shows considerable potential for human–computer interactions and wearable technologies. Furthermore, the sensor array can monitor real-time physiological signals of civil aviation pilots.

Researchers have been inspired by the movement and sensory abilities of animals in recent years due to the idea of soft robotics. This has resulted in the creation of biomimetic soft robots, which incorporate traits like biological vision and tactile sensation for use in manipulation, obstacle avoidance, and path planning. The miniaturization of soft robots has become a key area of research. However, their small size has limited their single locomotion capabilities, preventing true functional integration akin to that of biological systems. Inspired by the movement and electro-sensory abilities of insects in nature, this research developed a compact and lightweight (900 mg) electrothermal-driven (ETA) soft robot equipped with capacitive non-contact sensing. The electrothermal PE/CNT/PI composite film actuator exhibits excellent mechanical properties and flexibility, achieving a maximum bending angle of 320° and demonstrating a load capacity of at least 5 times its own weight. The sensor component consists of 0.2 mm diameter silver wire, which detects the proximity of objects through changes in the edge electric field. The signal response is highly sensitive and can effectively identify obstacles of various diameters. Compared to other reported works, this soft robot focuses on detecting the external environment, possessing the ability to sense obstacles in narrow spaces and dimly lit conditions. It also utilizes the generation of sensor signal changes during motion to obtain information about its own posture. This provides a new approach and basis for future applications in complex environments.

Oxygen vacancies play a vital role in the adsorption, activation, and subsequent reduction of CO₂ to methanol. This work presents the preparation of two-dimensional Bi₂WO₆ nanosheets with different oxygen vacancy concentrations (BWO-OV1, BWO-OV2, and BWO-OV3) and the evaluation of their catalytic activity in the photothermal catalytic reduction of CO₂ to methanol. The oxygen vacancy concentration has played a decisive role in controlling the methanol yield. The BWO-OV2 catalyst with the highest oxygen vacancy concentration (13.9%) accomplishes the maximum methanol yield (82.45 µmol/(g h)). This is because the oxygen vacancies enhance the adsorption and activation of CO₂ in the form of CO₂⁻, broaden the light adsorption range, and promote light-induced charge carrier separation. Also, BWO-OV2 exhibits 1.91 and 3.28 times higher catalytic activity in CO₂ reduction while being used under photothermal catalytic conditions than being employed under photocatalytic and thermal catalytic conditions, respectively. In line with the in-situ Fourier transform infrared spectroscopy and computational analysis, the external heat indiscriminately promotes the adsorption and further conversion of all involved intermediates but the light irradiation selectively enhances the adsorption of CO₂⁻, HCOO*, and CH₃O* species. The findings of the present work might provide key mechanistic insights into understanding the role of thermal and light irradiation in photothermal catalysis.

Magnetically responsive scaffolds are extensively utilized in tissue engineering for their ability to simulate dynamic three-dimensional (3D) cell microenvironment in a rapid, reversible, and contactless manner. However, existing magnetic scaffolds struggle to provide tunable dynamic compression comparable to natural tissues due to the weak magnetism of magnetic nanoparticles and the mechanical brittleness of hydrogels. Here, we propose a biomimetic 3D magnetic scaffold offering tunable and stable magnetically induced compression for dynamic 3D cell culture. By employing hard magnetic particles NdFeB@SiO₂ and a mechanically stable elastomer, Ecoflex, the scaffold achieves 15% compression in the magnetic field (240 mT). Moreover, this magnetic scaffold demonstrates remarkable deformation and mechanical stability during 4000 compression cycles. The magnetic scaffold exhibits stiffness (0.78 kPa) and viscoelasticity (relaxation time of 17 s) similar to adipose tissue. Notably, it is verified that human adipose-derived stem cells (hADSCs) are successfully cultured in this magnetic scaffold and the proliferation of hADSCs can be modulated by magnetically induced dynamic compression. This magnetic scaffold for dynamic 3D cell culture can be potentially utilized in cell biology and tissue engineering.